U.S. patent application number 10/967329 was filed with the patent office on 2005-08-25 for lens barrel and image taking apparatus.
This patent application is currently assigned to FUJINON CORPORATION. Invention is credited to Endo, Hiroshi, Omiya, Akio, Senba, Takehiko.
Application Number | 20050185289 10/967329 |
Document ID | / |
Family ID | 34865461 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050185289 |
Kind Code |
A1 |
Omiya, Akio ; et
al. |
August 25, 2005 |
Lens barrel and image taking apparatus
Abstract
A lens barrel has its length which is reduced by dispensing with
guide rods or a travel mechanism long extending from a base which
fixes an image pickup device. The optical axes of multiple lens
groups can be easily aligned. An image taking apparatus has its
body which has the lens barrel incorporated into it. A second lens
group, third lens group and, via the travel mechanism, a fourth
lens group are supported by a straight-ahead key ring, and the
straight-ahead key ring also supports a front tube holding the
first lens group. A zoom motor and a focus motor are also supported
by the straight-ahead key ring.
Inventors: |
Omiya, Akio; (Saitama,
JP) ; Senba, Takehiko; (Asaka, JP) ; Endo,
Hiroshi; (Asaka, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJINON CORPORATION
FUJI PHOTO FILM CO., LTD.
|
Family ID: |
34865461 |
Appl. No.: |
10/967329 |
Filed: |
October 19, 2004 |
Current U.S.
Class: |
359/695 |
Current CPC
Class: |
G02B 15/144 20190801;
G02B 7/102 20130101 |
Class at
Publication: |
359/695 |
International
Class: |
G02B 015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2004 |
JP |
2004-046617 |
Feb 23, 2004 |
JP |
2004-046628 |
Feb 23, 2004 |
JP |
2004-046630 |
Feb 23, 2004 |
JP |
2004-046638 |
Sep 24, 2004 |
JP |
2004-276740 |
Claims
What is claimed is:
1. A lens barrel which holds a zoom lens consisting of a plurality
of lens groups, the lens barrel comprising: a fixed tube, a
straight-ahead key member which is engaged with the fixed tube to
be able to advance or retract, a middle tube which is rotatably
engaged with the straight-ahead key member and is caused by cam
engagement with the fixed tube to advance or retract along with the
rotation; and a front tube which is engaged with the straight-ahead
key member to be able to advance or retract and is caused by cam
engagement with the middle tube to advance or retract along with
the rotation of the middle tube, wherein the zoom lens is
configured of a plurality of lens groups consisting of a first lens
group which is fixed to the front tube, a second lens group, a
third lens group and a fourth lens group which are fixed to the
straight-ahead key member or supported by the straight-ahead key
member to be able to advance or retract.
2. The lens barrel according to claim 1, wherein the second lens
group is supported by the straight-ahead key member to be able to
advance or retract and is caused by cam engagement with the middle
tube to advance or retract along with the rotation of the middle
tube.
3. The lens barrel according to claim 1, wherein the third lens
group is fixed to the straight-ahead key member.
4. The lens barrel according to claim 1, wherein the fourth lens
group is the focus lens, which is supported by the straight-ahead
key member via a travel mechanism for focusing.
5. The lens barrel according to claim 4, wherein the travel
mechanism is equipped with a focus motor which provides a driving
force to move the focus lens, and the focus motor is supported by
the straight-ahead key member.
6. The lens barrel according to claim 1, wherein a zoom motor is
provided to vary the zoom ratio of the zoom lens by rotationally
driving the middle tube, and the zoom motor is supported by the
straight-ahead key member.
7. The lens barrel according to claim 6, wherein the middle tube
has in part of its inner wall a row of gear teeth disposed in the
circumferential direction, and the zoom motor rotationally drives
the middle tube via a gear which links the rotation shaft of the
zoom motor and the row of gear teeth.
8. The lens barrel according to claim 1, wherein the middle tube
has cam pins which protrude from its outer wall surface and are
intended for cam engagement with the fixed tube, first cam grooves
which rotatably engage with the straight-ahead key member and
second cam grooves for cam engagement with the front tube, both
formed in its inner wall.
9. The lens barrel according to claim 8, wherein the first cam
grooves extend in the circumferential direction.
10. An image taking apparatus equipped with a lens barrel which
holds a zoom lens consisting of a plurality of lens groups and
takes a photograph by catching light incident from the subject via
the zoom lens held by the lens barrel, wherein the lens barrel
comprises a fixed tube, a straight-ahead key member which is
engaged with the fixed tube to be able to advance or retract, a
middle tube which is rotatably engaged with the straight-ahead key
member and is caused by cam engagement with the fixed tube to
advance or retract along with the rotation, and a front tube which
is engaged with the straight-ahead key member to be able to advance
or retract and is caused by cam engagement with the middle tube to
advance or retract along with the rotation of the middle tube; the
zoom lens being configured of a plurality of lens groups consisting
of a first lens group which is fixed to the front tube, a second
lens group, a third lens group and a fourth lens group which are
fixed to the straight-ahead key member or supported by the
straight-ahead key member to be able to advance or retract.
11. The image taking apparatus according to claim 10, wherein the
lens barrel is equipped with a focus motor which provides a driving
force to a travel mechanism to move the focus lens, and the focus
motor is supported by the straight-ahead key member.
12. The image taking apparatus according to claim 10, wherein the
lens barrel is further provided with a zoom motor which varies the
zoom ratio of the zoom lens by rotationally driving the middle
tube, and the zoom motor is supported by the straight-ahead key
member.
13. The image taking apparatus according to claim 10, wherein the
middle tube has cam pins which protrude from its outer wall surface
and are intended for cam engagement with the fixed tube, first cam
grooves which rotatably engage with the straight-ahead key member
and second cam grooves for cam engagement with the front tube, both
formed in its inner wall.
14. The image taking apparatus according to claim 10, further
provided with an image pickup device which generates an image
signal by catching light incident from the subject via the zoom
lens held by the lens barrel.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a lens barrel which holds a
zoom lens consisting of multiple lens groups as well as to an image
taking apparatus which is provided with the lens barrel and takes
images by capturing light from a subject entering through the zoom
lens held by the lens barrel.
[0003] 2. Description of the Related Art
[0004] Today, digital cameras are in rapidly expanding use, and
they are required to provide ever higher image quality along with
reductions in overall size and profile thickness. As a digital
camera to meet these requirements, there is proposed a thin
visiting card-size digital camera equipped with a lens barrel
holding a zoom lens consisting of multiple lens groups (see
non-patent literature 1, Internet URL
http://www.business-ijp/sentan/jusyou/2003/pentax/) and is already
commercially available. This digital camera permits zooming with
high image quality with an optical zoom while earlier thin digital
cameras use an electronic zooming function to achieve a high degree
of magnification.
[0005] One of the notable needs of users is equipment with such an
optical zoom capable of zooming at an even higher magnification
while realizing further reductions in size and profile
thickness.
[0006] Patent Document 1 (Japanese Patent Laid-Open No.
2003-295031) proposes a technique for collapsing a lens barrel
equipped with a zoom lens into a thin camera body by contriving an
improved way of forming cam grooves.
[0007] The internal configuration of the lens barrel disclosed in
this patent literature 1 is described below.
[0008] FIGS. 1, 2 and 3 are sections taken along the optical axis
of a lens barrel built into a digital camera. Of these FIGS. 1
through 3, FIGS. 1 and 2 show the lens barrel in its extended
state. Incidentally, patent literature 1 states that FIG. 1 shows a
telephoto end and FIG. 2, a wide-angle end. FIG. 3 shows the lens
barrel in its collapsed state. Further, FIG. 4 is a developed view
illustrating cam grooves which function when the lens barrel is
extended out or collapses into the camera body.
[0009] The configuration of this lens barrel 100 is described below
with reference to FIG. 1 through FIG. 4.
[0010] This lens barrel 100 holds a zoom lens of a four-group
configuration consisting of a first lens group 210, a second lens
group 220, a third lens group 230 and a fourth lens group 240. By
moving the second lens group 220, out of these four lens groups, in
the direction of the optical axis, the focal distance is adjusted,
and moving the fourth lens group 240, serving as the focus lens, in
the direction of the optical axis, focusing is accomplished.
[0011] The first lens group 210 is held in an inner tube 110. This
inner tube 110 is provided with cam pins 111, and these cam pins
111 engaged with cam grooves 121 formed in the inner surface of an
outer tube 120 (see FIG. 4). Three such cam pins 111 are disposed
at unequal intervals on the outer wall of the inner tube 110, and
three cam grooves 121 to engage with those cam pins 111 are formed
at unequal intervals in the inner wall of the outer tube 120 (see
FIG. 4). Therefore, when the rotation of a zoom motor 270 is
transmitted from a coupling gear 271 (see FIG. 2) to a gear 124
disposed on the inner wall of the outer tube 120 to turn the outer
tube 120, the first lens group 210 extends together with the inner
tube 110 along the shape of the cam grooves 121.
[0012] The second lens group 220 is held by a lens group holding
frame 221, and three cam pins 222 are disposed at unequal intervals
on the circumference of that lens group holding frame 221. Those
cam pins 222 engage with respective cam grooves 122 formed in the
inner wall of the outer tube 120 (see FIG. 4). A guide rod 1132 is
passed through a through-hole 221a formed in the lens group holding
frame 221 of the second lens group 220. When the outer tube 120
turns, the second lens group 220, guided by that guide rod 1132,
moves in the direction of the optical axis. The guide rod 1132 is
held by a tip support 1132a, and a guide rod 1133 to guide the
movement of the third lens group 230 is supported by another tip
support 1133a. These tip supports 1132a and 1133a, besides
respectively supporting the two guide rods 1132 and 1133, are also
used as members to support the inner tube 110. These tip supports
1132a and 1133a are equipped with an intermediate frame 1101 and a
retainer ring 1102. The intermediate frame 1101 is inserted
slidably along the inner wall of the inner tube 110, while the
retainer ring 1102 is provided at the rear end of that inner tube
110 to prevent the intermediate frame 1101 from moving backward.
The intermediate frame 1101 and the retainer ring 1102 are
respectively equipped with spring pegs 1101a and 1102b. When the
intermediate frame 1101 is extended together with the inner tube
110, a spring 1103 bridging those spring pegs urges the
intermediate frame 1101 forward along the sliding surface to
restrict the movement of the intermediate frame 1101 not to let the
intermediate frame 1101 move backward.
[0013] Further, one cam groove 123 (see FIG. 4) to engage with cam
pins (not shown) disposed on a lens group holding frame 130 of the
third lens group 230 is formed in the outer tube 120 between the
cam grooves 121 and 122. Therefore, when the outer tube 120 turns,
receiving the driving force of the zoom motor 270 via the coupling
gear 271 and the gear 124 (see FIG. 2), the third lens group 230
also moves in the direction of the optical axis along the shape of
the cam groove 123. A shutter unit 131 is linked to the lens group
holding frame 130 holding this third lens group 230.
[0014] A through-hole 131a is formed in this lens group holding
frame 130, too, as in the lens group holding frame 221, and the
guide rod 1132 is passed through this through-hole 131a. Further,
the guide rod 1132 is also passed through a through-hole 141a
formed in a lens group holding frame 140, to be described after
wards, for holding the fourth lens group 240. In this way, the
example taken up here has a configuration in which the second lens
group 220, the third lens group 230 and the fourth lens group 240
are guided in movement by the common guide rod 1132 to prevent the
optical axis from misalignment.
[0015] The extending operation of the lens barrel 100 having such a
structure is described in detail with reference to FIG. 4.
[0016] When the outer tube 120 rotates driven by the zoom motor
270, the inner tube 110 is extended from a collapsed state along
the shape of the cam grooves 121 (the area marked with symbol A) to
its extended position (the end toward symbol B of the area marked
with symbol A), and held in that extended position (the area marked
with symbol B). Until the outer tube 120 is held in this extended
position, the second lens group 220 moves in the area marked with
symbol C along the shape of the cam grooves 122, and reaches the
end of the area marked with symbol C when the inner tube 110 has
been extended to its extended position. When a zoom switch (not
shown) is operated then, the second lens group 220 enters into the
area marked with symbol D according to the operation of that zoom
switch. If the zoom switch continues to be operated, it will reach
the end of the symbol D area. On the other hand, when the outer
tube 120 is turned, the third lens group 230 moves from its
collapsed position in the extending area (the area marked with
symbol E) along the cam groove 123 to reach its extended position
(the intersection between symbol E and symbol F) and, even if the
zoom switch is operated, remains held in that extended position
(the area marked with symbol F).
[0017] By arranging the cam grooves effectively in the inner wall
of the outer tube 120 in this way, it is made possible to move the
first lens group 210, the second lens group 220 and the third lens
group 230 out of the four lens groups in the direction of the
optical axis along the shapes of the cam grooves by the rotation of
the single tube 120, and to perform zooming by moving the second
lens group in the direction of the optical axis according to the
operation of the zoom switch.
[0018] In the lens barrel 100 shown in FIGS. 1 through 3, the
aftermost fourth lens group 240 out of the four lens groups
constituting the zoom lens is used as the focus lens. Since this
zoom lens held by the lens barrel 100 has a high zoom ratio, the
traveling distance of the fourth lens group 240 to function as its
focus lens should be relatively long. Therefore in this example, a
column screw 1131 (see FIG. 1) having a length equal to that long
traveling distance is disposed along the optical axis, a nut 141b
is fixed to the lens group holding frame 140 holding the fourth
lens group 240, and the column screw 1131 is screwed into that nut
141b to enable focusing to be accurately accomplished.
[0019] The rotational driving force of a focus motor (not shown) is
transmitted to this column screw 1131 via a gear train (not shown)
to rotate this column screw 1131 and, along with that rotation, a
lens group holding frame 141 guided by the column screw 1131 and
the guide rods 1132 and 1133 moves in the direction of the optical
axis correspondingly to the rotation of the column screw 1131 to
perform focusing. When an image taking lens begins catching a
subject, image data are generated by an image pickup device 280,
the focus position is detected on the basis of the image data, and
focusing is performed by turning the column screw to move the
fourth lens group 240, which serves as the focus lens, to that
detected focus position.
[0020] If a shutter button (not shown) is pressed after focusing is
accomplished, the shutter unit 131 arranged on the lens group
holding frame 130 holding the third lens group 230 is driven in
synchronism with full pressing of the shutter button to take an
image. Light from the subject having passed the first lens group
210, the second lens group 220, the third lens group 230 and the
fourth lens group (focus lens) 240 forms an image on the
light-receiving surface of the image pickup device 280, and this
image pickup device 280 generates an image signal which represents
the image of the subject formed on that light-receiving
surface.
[0021] By arranging the multiple cam grooves effectively in the
inner wall of the outer tube in this way, bringing them into cam
engagement with the inner tube, and causing the aftermost lens
group of the zoom lens to function as the focus lens, the length of
the lens barrel in the collapsed state is reduced to relative
compactness to be accommodable in a relatively thin body, and a
lens barrel which can achieve a high zoom ratio when extended is
thereby realized.
[0022] However, the configuration described above in which the
travel of the second lens group 220, the third lens group 230 and
the fourth lens group 240 is guided by the common guide rod 1132
extending over a great length from the light-receiving surface of
the image pickup device imposes a limit to the thinning of the
profile.
[0023] Apart from that, patent literature 2 (Japanese Patent
Laid-Open No. 6-67076) discloses a three-group zoom lens barrel
which can provide a long traveling distance for lenses at a small
angle of rotation of a cam ring.
[0024] According to this patent literature 2, though there is no
guide rod or the like extending over a great length from a base
which fixes an image pickup device, the second and third groups out
of the three lens groups, prevented from rotating by a
straight-ahead key, move in the direction of the optical axis via a
cam mechanism, and supported only via that cam mechanism.
Accordingly, it is extremely difficult to adjust the optical axis
with high precision and, if this technique is applied to a zoom
lens of a four lens-group configuration, adjustment of the optical
axis and keeping its accuracy will be extremely difficult, making
it prohibitively difficult to extend this technique as it is to a
four lens-group configuration.
SUMMARY OF THE INVENTION
[0025] The present invention has been made in view of the above
circumstances and provides a lens barrel in which the optical axes
of lens groups can be readily aligned even if its length is
shortened by dispensing with a guide rod long extending from a base
which fixes an image pickup device, and an image taking apparatus
into whose body the lens barrel is incorporated.
[0026] To achieve the objected stated above, the present invention
provides a lens barrel which holds a zoom lens consisting of
multiple lens groups, the lens barrel including:
[0027] a fixed tube, a straight-ahead key member which is engaged
with the fixed tube to be able to advance or retract, a middle tube
which is rotatably engaged with the straight-ahead key member and
is caused by cam engagement with the fixed tube to advance or
retract along with the rotation; and a front tube which is engaged
with the straight-ahead key member to be able to advance or retract
and is caused by cam engagement with the middle tube to advance or
retract along with the rotation of the middle tube, wherein
[0028] the zoom lens is configured of multiple lens groups
consisting of a first lens group which is fixed to the front tube,
a second lens group, a third lens group and a fourth lens group
which are fixed to the straight-ahead key member or supported by
the straight-ahead key member to be able to advance or retract.
[0029] In the lens barrel according to the invention, out of the
constituent groups of the zoom lens, all of the second lens group,
third lens group and fourth lens group are fixed to the
straight-ahead key member or supported by the straight-ahead key
member to be able to advance or retract, and the first lens group
is fixed to the front tube engaged with the straight-ahead key
member to be able to advance or retract. Where all of the second
lens group, third lens group and fourth lens group are mounted on
the straight-ahead key member, the optical axes can be aligned with
high precision, there can be realized a lens barrel in which the
optical axes of the multiple lens groups can be easily aligned even
if a reduction in length is attempted by dispensing with guide rods
or the travel mechanism long extending from the base which fixes
the image pickup device.
[0030] It is preferable here for the second lens group to be
supported by the straight-ahead key member to be able to advance or
retract and caused by cam engagement with the middle tube to
advance or retract along with the rotation of the middle tube.
[0031] It is preferable for the third lens group to be also fixed
to the straight-ahead key member.
[0032] It is also preferable for the fourth lens group to be the
focus lens and to be supported by the straight-ahead key member via
a travel mechanism for focusing, for that travel mechanism to be
equipped with a focus motor which provides a driving force to move
the focus lens, and for the focus motor to be supported by the
straight-ahead key member.
[0033] Then, when extending the lens barrel, the third lens group
supported by the straight-ahead key member, together with the
middle tube, moves in the direction of the optical axis to be
arranged in its prescribed position, and the fourth lens group is
also arranged in its own prescribed position along with travel of
that straight-ahead key member in the direction of the optical
axis. If this prescribed position is set in the vicinity of the
in-focus position of this zoom lens, focusing can be accomplished
by having the travel mechanism the position of the fourth lens
group, which is in the vicinity of that in-focus position.
[0034] It is also preferable for a zoom motor to be provided to
vary the zoom ratio of the zoom lens by rotationally driving the
middle tube, and the zoom motor to be supported by the
straight-ahead key member. It is further preferable for the middle
tube to have in part of its inner wall a row of gear teeth disposed
in the circumferential direction, and for the zoom motor
rotationally to drive the middle tube via a gear which links the
rotation shaft of the zoom motor and the row of gear teeth.
[0035] It is also preferable for the middle tube to have cam pins
which protrude from its outer wall surface and are intended for cam
engagement with the fixed tube, first cam grooves which rotatably
engage with the straight-ahead key member and second cam grooves
for cam engagement with the front tube, both formed in its inner
wall, and it is also preferable for those first cam grooves to
extend in the circumferential direction.
[0036] Then, by turning according to the operation of the zoom
switch the middle tube by the use of the zoom motor supported by
the straight-ahead key member, zooming can be accomplished by
moving the second lens group in the direction of the optical
axis.
[0037] The present invention also provides an image taking
apparatus equipped with a lens barrel which holds a zoom lens
consisting of multiple lens groups and takes an image by catching
light incident from the subject via the zoom lens held by the lens
barrel, wherein
[0038] the lens barrel includes a fixed tube, a straight-ahead key
member which is engaged with the fixed tube to be able to advance
or retract, a middle tube which is rotatably engaged with the
straight-ahead key member and is caused by cam engagement with the
fixed tube to advance or retract along with the rotation, and a
front tube which is engaged with the straight-ahead key member to
be able to advance or retract and is caused by cam engagement with
the middle tube to advance or retract along with the rotation of
the middle tube;
[0039] the zoom lens being configured of multiple lens groups
consisting of a first lens group which is fixed to the front tube,
a second lens group, a third lens group and a fourth lens group
which are fixed to the straight-ahead key member or supported by
the straight-ahead key member to be able to advance or retract.
[0040] The image taking apparatus according to the invention is
equipped with a lens barrel having a built-in zoom lens which has
no distortion in optical axis and excels in optical
characteristics. Therefore, high-definition image taking can be
accomplished with this image taking apparatus.
[0041] It is preferable here for the lens barrel to be equipped
with a focus motor which provides a driving force to a travel
mechanism to move the focus lens, and the focus motor to be
supported by the straight-ahead key member. It is further
preferable here for the lens barrel to be further provided with a
zoom motor which varies the zoom ratio of the zoom lens by
rotationally driving the middle tube, and the zoom motor to be
supported by the straight-ahead key member.
[0042] It is also preferable for the middle tube to have cam pins
which protrude from its outer wall surface and are intended for cam
engagement with the fixed tube, first cam grooves which rotatably
engage with the straight-ahead key member and second cam grooves
for cam engagement with the front tube, both formed in its inner
wall.
[0043] Then, an image taking apparatus having a compact lens barrel
whose middle tube serves as the driving tube can be realized.
[0044] It is also preferable for the image taking apparatus to be
further provided with an image pickup device which generates an
image signal by catching light incident from the subject via the
zoom lens held by the lens barrel.
[0045] Where such an image pickup device is provided, a further
enhancement in zoom ratio can be achieved by performing electronic
zooming by using the image pickup device in addition to optical
zooming.
[0046] As hitherto described, there are realized a lens barrel in
which the optical axes of the multiple lens groups can be easily
aligned even if a reduction in length is attempted by dispensing
with guide rods or the travel mechanism long extending from the
base which fixes the image pickup device, and an image taking
apparatus whose body has the lens barrel incorporated into it.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a sectional view taken along the optical axis of a
lens barrel built into a conventional digital camera in a state in
which the lens barrel is at a wide-angle end;
[0048] FIG. 2 is a sectional view taken along the optical axis of
the lens barrel built into the conventional digital camera in a
state in which the lens barrel is at a telephoto end;
[0049] FIG. 3 is a sectional view taken along the optical axis of
the lens barrel built into the conventional digital camera in a
state in which the lens barrel is collapsed;
[0050] FIG. 4 is a developed view illustrating cam grooves formed
in the inner wall of an outer tube 120 and used for adjusting the
focal distance by extending an inner tube 110 as well as
controlling the distance between a second lens group 220 and a
third lens group 230;
[0051] FIG. 5 is an external perspective view of a digital camera
300, which is an embodiment of an image taking apparatus according
to the present invention and which incorporates an embodiment of a
lens barrel according to the invention;
[0052] FIG. 6 shows a state in which the lens barrel of the digital
camera shown in FIG. 5 is extended;
[0053] FIG. 7 is a sectional view taken along the optical axis of a
lens barrel 310 incorporated into the digital camera shown in FIGS.
5 and 6 in a state in which the lens barrel is at the wide-angle
end;
[0054] FIG. 8 is a sectional view taken along the optical axis of
the lens barrel 310 incorporated into the digital camera shown in
FIGS. 5 and 6 in a state in which the lens barrel is at the
telephoto end;
[0055] FIG. 9 is a sectional view taken along the optical axis of
the lens barrel 310 incorporated into the digital camera shown in
FIGS. 5 and 6 in a state in which the lens barrel is collapsed;
[0056] FIG. 10 shows the lens barrel sliced along the line and
viewed in the direction of the arrows in FIG. 7;
[0057] FIG. 11 shows the lens barrel sliced along the line and
viewed in the direction of the arrows in FIG. 8;
[0058] FIG. 12 is a developed view illustrating cam grooves formed
in the inner wall of a middle tube; and
[0059] FIG. 13 is a block diagram showing the circuit configuration
of the digital camera of this embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0060] An embodiment of the present invention is described
below.
[0061] FIGS. 5 and 6 are external perspective views of a digital
camera, which is an embodiment of an image taking apparatus
according to the present invention and which incorporates an
embodiment of a lens barrel according to the invention.
[0062] FIG. 5 is an external view of a lens barrel 310 incorporated
into this digital camera 300 when it is in a collapsed state, and
FIG. 6 is an external view of that lens barrel 310 when it is in an
extended state.
[0063] The lens barrel 310 of the digital camera 300 shown in FIGS.
5 and 6 has an image taking lens consisting of four lens groups
built into it which is to be described afterwards. By moving a
second lens group out of those four lens groups in the direction of
the optical axis, the focal distance is adjusted, and by moving a
fourth lens group as the focus lens in the direction of the optical
axis, focusing is performed.
[0064] In the upper front part of the digital camera 300 shown in
FIGS. 5 and 6, a fill flash window 302 and a finder objective
window 303 are arranged. Further, a shutter button 304 is arranged
on the top face of this digital camera 300.
[0065] A zoom control switch is disposed on the back (not shown) of
this digital camera 300. While one end of this zoom control switch
is kept pressed, the lens barrel 310 extends to the telephoto side.
While the other end of the zoom control switch is kept pressed, the
lens barrel 310 moves to the wide-angle side.
[0066] FIGS. 7, 8 and 9 are sectional views taken along the optical
axis of the lens barrel 310 incorporated into the digital camera
shown in FIGS. 5 and 6. These FIGS. 7, 8 and 9 respectively show
the wide-angle, telephoto end and collapsed state. FIG. 10 is a
sectional view of the lens barrel in the state shown in FIG. 7,
sliced and viewed in the direction of arrows A-A' in FIG. 7, and
FIG. 11 is a sectional view of the lens barrel in the state shown
in FIG. 8, sliced and viewed in the direction of arrows B-B' in
FIG. 8. FIG. 7 is a sectional view along arrows C-C' shown in FIG.
10, and FIG. 8 is a sectional view along arrows D-D' shown in FIG.
11. Further, FIG. 12 is a developed view illustrating cam grooves
formed in the inner walls of the outermost and middle tubes out of
the three tubes constituting the lens barrel shown in FIG. 7
through FIG. 11. In the following description, the outermost tube
of the three tubes is referred to as a fixed tube 313, the middle
tube as a middle tube 312, and the innermost tube as a front tube
311.
[0067] A zoom lens of a four-group configuration consisting of a
first lens group 410, second lens group 420, third lens group 430
and fourth lens group 440 is incorporated into this lens barrel
310. The fourth lens group 440 at the tail of this zoom lens of the
four-group configuration is used as the focus lens.
[0068] As shown in FIGS. 7, 8 and 9, the first lens group 410 is
held in the front tube 311, and this front tube 311 is equipped
with cam pins 3111 (see FIG. 8). These campins 3111 are engaged
with cam grooves 3123 (see FIGS. 8 and 12) formed in the inner wall
of the middle tube 312. The middle tube 312 is also equipped with
cam pins 3124, and those cam pins 3124 are engaged with cam grooves
3131 (see FIG. 12) formed in the inner wall of the fixed tube 313.
A straight-ahead key ring 320 is so configured as to protrude
toward the front tube 311, and its end on that protruding side
engages with the front tube 311 to serve to stop the rotation of
the front tube. Therefore, the front tube 311 and the
straight-ahead key ring 320 are capable only of relative travel in
the direction of the optical axis, but not of rotation around the
optical axis.
[0069] The middle tube 312 here is so configured as to be rotated
by a zoom motor 3300 (see FIG. 9). As the middle tube 312 rotates
driven by the zoom motor 3300, the middle tube 312 moves, while
rotating, in the direction of the optical axis along the shape of
the cam grooves 3131 in the inner wall of the fixed tube 313. The
front tube 311 moves in cam engagement with that rotating and
moving middle tube 312 in the direction of the optical axis along
the shape of the cam grooves 3123. FIGS. 9, 10 and 11 show how the
zoom motor and the middle tube are coupled with each other. The
figures show the configuration in which a turning force is
transmitted to a gear 3125 disposed on the inner wall of the middle
tube 312 from the zoom motor 3300 via a coupling gear 3302 and the
middle tube 312 is thereby turned.
[0070] A straight-ahead key 320K disposed on the straight-ahead key
ring 320 is engaged with a straight-ahead groove 3132 formed in the
fixed tube 313 to be able to advance and retract. Engagement of cam
pins 3203 disposed on this straight-ahead key ring 320 with cam
grooves 3122 (see FIGS. 8 and 12) formed in the middle tube 312 and
extending in the circumferential direction causes the middle tube
312 to rotatably engage with the straight-ahead key ring 320.
Therefore, as this middle tube 312 is caused to advance or retract
by its cam engagement with the fixed tube 313, the straight-ahead
key ring 320 also advances or retracts together with the middle
tube 312.
[0071] In this way, the middle tube 312 is capable of relative
rotation around the optical axis, and of moving in the direction of
the optical axis integrally with the straight-ahead key ring 320.
The zoom motor 3300 is supported by that straight-ahead key ring
320. When the middle tube 312 is advancing or retracting in the
direction of the optical axis together with that straight-ahead key
ring 320, the rotation of the zoom motor 3300 supported by that
advancing or retracting straight-ahead key ring 320 is transmitted
to the middle tube 312 via a gear 3302, and the middle tube 312 is
thereby driven to rotate. Then the gear linking section between the
zoom motor 3300 and the middle tube is significantly shortened,
resulting in a simple structure. Therefore, it is made possible to
reduce the size of the zoom motor supported by the straight-ahead
key ring, thereby allowing the lens barrel to be reduced in size by
disposing that compact zoom motor within the lens barrel.
[0072] Regarding the lens groups holding frames holding the lens
groups, the relationship among a lens group holding frame 421
holding the second lens group 420, a lens group holding frame 441
holding the fourth lens group 440 and the middle tube 312, the
relationship between the straight-ahead key ring 320 and the third
lens group 430, and the relationship between the middle tube 312
and the fixed tube 313 are now described in detail with reference
to FIGS. 7 through 12.
[0073] First, the lens group holding frame 421 holding the second
lens group 420 is equipped with cam pins 3211 on its outer wall.
Those cam pins 3211 engage with cam grooves 3121 (see FIGS. 7 and
12) formed in the inner wall of the middle tube 312. Further as
shown in FIGS. 7 through 11, the straight-ahead key ring 320
supports the second lens group 420 via two guide rods 321 and 322,
supports the third lens group 430, and supports the fourth lens
group 440 via a travel mechanism consisting of a column screw 3201
(see FIG. 8). The lens group holding frame 421 supporting the
second lens group 420 is provided with two through-holes 421a and
421b, and the two guide rods 321 and 322 supported by the
straight-ahead key ring 320 penetrate those through-holes 421a and
421b. The cam pins 3211 of the lens group holding frame 421 are
positioned in the vicinity of the through-hole 421a out of those
through-holes, and those cam pins 3211 engage with the cam grooves
3121 of the middle tube 312. As these cam pins 3211 travel along
the shape of the cam grooves 3121, the second lens group 420,
guided by the two guide rods 321 and 322, moves from the telephoto
end to the wide-angle end or from the wide-angle end to the
telephoto end.
[0074] The middle tube 312 is equipped with the cam pins 3124
implanted on its outer wall, and those cam pins 3124 engage with
the cam grooves 3131 formed in the inner wall of the fixed tube
313. These cam grooves 3131 so extend as to rotate by a prescribed
angle (the area marked with symbol k in FIG. 12) during extension
from the collapsed state shown in FIG. 9 to the telephoto end shown
in FIG. 8. Therefore the middle tube 312, receiving the driving
force from the zoom motor 3300 (see FIG. 9), is extended in the
direction of the optical axis while rotating by a prescribed angle
following those cam grooves 3131 during its travel from the
collapsed state (FIG. 9) to the telephoto end (FIG. 8), and along
with that extension of the middle tube 312 the front tube 311 is
extended along the shape of the cam grooves 3123 (the area marked
with symbol m in FIG. 12) without rotating. If the zoom switch is
operated toward the wide-angle side when the middle tube 312 is in
this extended state, the middle tube 312 rotates in that position
(the area marked with symbol l in FIG. 12), and the rotation causes
the second lens group 420 to move to the wide-angle end along the
shape of the cam grooves 3121 (the area marked with symbol p in
FIG. 12). In this way, zooming is accomplished according to the
operation of the zoom switch.
[0075] The third lens group 430 is supported by the straight-ahead
key ring 320, and that straight-ahead key ring 320 also supports
the fourth lens group 440 via a travel mechanism consisting of a
focus motor 3200 (see FIG. 8) and the column screw 3201 meshed with
the gear train 3202 of that focus motor 3200. This fourth lens
group 440 is held by the lens group holding frame 441, and the lens
group holding frame 441 is equipped with a fork 441a, and a guide
rod 3205 disposed on the straight-ahead key ring 320 engages with
that fork 441a. A nut 441b into which the column screw 3201 is to
be screwed is fixed to the lens group holding frame 441, and the
column screw 3201 supported by the straight-ahead key ring 320 is
screwed into that nut 441b.
[0076] On the other hand, the focus motor 3200 for moving the
fourth lens groups in the direction of the optical axis is also
supported by the straight-ahead key ring 320, and the rotational
driving force of the focus motor 3200 supported by the
straight-ahead key ring 320 is transmitted to the column screw 3201
shown in FIG. 8 via a gear train 3202 to rotate this column screw
3201. Along with this rotation, the lens group holding frame 421,
guided by the column screw 3201 and the guide rod 3205, travels in
the direction of the optical axis correspondingly to the extent of
rotation of the column screw 3201, and focusing is thereby
performed. This focusing is performed in accordance with a driving
instruction issued to the focus motor 3200 on the basis of image
data generated by an image pickup device 500.
[0077] If the shutter button 304 is pressed after focusing is
accomplished in this way, a shutter unit 330 supported by the
straight-ahead key ring is driven, and an electronic shutter
release is driven to take an image. As a result, light from the
subject having passed the first lens group 410, second lens group
420, third lens group 430 and fourth lens group (focus lens) 440
forms an image on the light-receiving surface of the image pickup
device 500, and an image signal representing that subject image
formed on that light-receiving surface is generated by the image
pickup device 500. Incidentally, wiring cables for transmitting
instructions to the focus motor or the shutter unit are not shown
in FIGS. 7 through 11.
[0078] By causing in this way the straight-ahead key ring 320
traveling in direction of the optical axis to support the second
lens group 420 and the third lens group 430 and, via the column
screw 3201, the fourth lens group 440, and further the focus motor
3200 rotating that column screw 3201 and the zoom motor 3300
rotationally driving the middle tube 312, the optical axes can be
kept accurate to match the linearity of the straight-ahead key
ring.
[0079] In this way, there is no need for guide rods, long extending
as shown in FIG. 1, provided to correct any misalignment of the
optical axes of the second lens group 420, third lens group 430 and
fourth lens group 440, and a free space is left between the image
pickup device 500 and the fourth lens group 440. As all the lenses
can be stowed into that free space when the lens barrel is
collapsed, the lens barrel can be reduced in length. Also, the
first cam grooves 3122 shown in FIG. 12 are disposed in the
circumferential direction of the middle tube 312 to rotatably
engage the straight-ahead key ring with the middle tube 312, the
straight-ahead key ring 320 is also moved along with the travel of
the middle tube 312, and at the same time the front tube 311 is
extended along the second cam grooves 3123 as much as the length of
the middle tube 312. The lens barrel is thereby extended in length,
namely increased in zoom ratio. Furthermore, when the lens barrel
is collapsed, its length can be reduced to no greater than the
length of the middle tube 312, making it possible to reduce the
profile thickness of the body.
[0080] Therefore, the body of the digital camera 300 shown in FIGS.
5 and 6 is thin in profile thickness because the lens barrel 310
can be accommodated within the camera body when it is collapsed.
When an image is to be taken, the lens barrel 310 holding the zoom
lens of a four-group configuration is extended to a great extent
out of the camera body to enable the user to enjoy image taking at
a high zoom ratio with this digital camera 300. Finally, the
internal configuration of the digital camera shown in FIGS. 5 and 6
is briefly described.
[0081] FIG. 13 is a block diagram shown the circuit configuration
of the digital camera of this embodiment.
[0082] This digital camera 300 is equipped with a zoom lens 400 of
a four-group configuration consisting of the first lens group 410,
second lens group 420, third lens group 430 and fourth lens group
440, the shutter unit 330 and the image pickup device 500, all
shown in FIGS. 7 through 9. A subject image formed on the image
pickup device 500 via the zoom lens 400 and shutter unit 330 is
converted into an analog image signal by the image pickup device
500. The shutter unit 330 here is configured of an aperture for
limiting the quantity of light irradiating the image pickup device
and a shutter which prevents smearing caused by light when the
analog image signal is read out of the image pickup device 500.
[0083] Here is also provided a fill flash section 600. This fill
flash section 600, through a fill flash window shown in FIGS. 5 and
6, emits supplementary light ahead of the digital camera in
low-light conditions. The fill flash section 600 can also be caused
to emit as required if not in low-light conditions.
[0084] This digital camera 300 is further equipped with an analog
signal processing section 501, A/D converter section 502, digital
signal processing section 503, temporary memory 504,
compression/decompression section 505, built-in memory (or memory
card) 506, image monitor 507 and drive circuit 508. The solid image
pickup device 500 is driven at timings generated by a timing
generation circuit (not shown) in the drive circuit 508, and
outputs an analog image signal. The drive circuit 508 also includes
drive circuits which drive an image taking lens 400, shutter unit,
fill flash section 600 and so forth. The analog image signal
outputted from the image pickup device 500 undergoes analog signal
processing by the analog signal processing section 501, A/D
conversion by the A/D converter section 502, and digital signal
processing by the digital signal processing section 503. Image data
representing the image after the digital signal processing are
temporarily stored into the temporary memory 504. The image data
stored into the temporary memory 504 are compressed by the
compression/decompression section 505 and recorded into the
built-in memory (or memory card) 506. Depending on the image pickup
mode, the compression process can be dispensed with and the data
can be directly recorded into the built-in memory (or memory card)
506. The image data stored into the temporary memory 504 are read
out to the image monitor 507 to display the image of the subject on
the image monitor 507.
[0085] This digital camera 300 is further equipped with a CPU 509
for exercising overall control over this digital camera 300,
control switch group 510 including a zoom control switch, and the
shutter button 304. By setting the camera to a desired image taking
conditions including the setting of a desired angle of view by
operating the control switch group 510 and pressing down the
shutter button 304, a photograph is taken, i.e. the image data
described above are generated.
* * * * *
References